A scalar quantity is a physical measurement that is described by a single numerical value and a unit. It does not have a direction associated with it, making it simpler to understand and work with. Common examples of scalar quantities include temperature, mass, and time. These quantities can be fully described by their magnitude alone. In contrast to scalar quantities, vector quantities have both magnitude and direction. For instance, while speed is a scalar quantity, velocity is a vector quantity because it includes both the speed of an object and the direction in which it is moving. Understanding the difference between these two types of quantities is essential in physics and engineering.